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RFC 822

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RFC # 822

Obsoletes: RFC #733 (NIC #41952)

### STANDARD FOR THE FORMAT OF

ARPA INTERNET TEXT MESSAGES

August 13, 1982

Revised by

David H. Crocker

Dept. of Electrical Engineering
University of Delaware, Newark, DE 19711
Network: DCrocker @ UDel-Relay

### Table of Contents

1. INTRODUCTION

1.1. SCOPE
1.2. COMMUNICATION FRAMEWORK

2. NOTATIONAL CONVENTIONS

2.1. RULE NAMING
2.2. RULE1 / RULE2: ALTERNATIVES
2.3. (RULE1 RULE2): LOCAL ALTERNATIVES
2.4. *RULE: REPETITION
2.5. [RULE]: OPTIONAL
2.6. NRULE: SPECIFIC REPETITION
2.7. #RULE: LISTS
2.8. ; COMMENTS

3. LEXICAL ANALYSIS OF MESSAGES

3.1. GENERAL DESCRIPTION

3.1.1. LONG HEADER FIELDS
3.1.2. STRUCTURE OF HEADER FIELDS
3.1.3. UNSTRUCTURED FIELD BODIES
3.1.4. STRUCTURED FIELD BODIES

3.2. HEADER FIELD DEFINITIONS
3.3. LEXICAL TOKENS
3.4. CLARIFICATIONS

3.4.1. QUOTING
3.4.2. WHITE SPACE
3.4.3. COMMENTS
3.4.4. DELIMITING AND QUOTING CHARACTERS
3.4.5. QUOTED-STRINGS
3.4.6. BRACKETING CHARACTERS
3.4.7. CASE INDEPENDENCE
3.4.8. FOLDING LONG HEADER FIELDS
3.4.9. BACKSPACE CHARACTERS
3.4.10. NETWORK-SPECIFIC TRANSFORMATIONS

4. MESSAGE SPECIFICATION

4.1. SYNTAX
4.2. FORWARDING
4.3. TRACE FIELDS

4.3.1. RETURN-PATH
4.3.2. RECEIVED

4.4. ORIGINATOR FIELDS

4.4.1. FROM / RESENT-FROM
4.4.2. SENDER / RESENT-SENDER
4.4.3. REPLY-TO / RESENT-REPLY-TO
4.4.4. AUTOMATIC USE OF FROM / SENDER / REPLY-TO

4.5. RECEIVER FIELDS

4.5.1. TO / RESENT-TO
4.5.2. CC / RESENT-CC
4.5.3. BCC / RESENT-BCC

4.6. REFERENCE FIELDS

4.6.1. MESSAGE-ID / RESENT-MESSAGE-ID
4.6.2. IN-REPLY-TO
4.6.3. REFERENCES
4.6.4. KEYWORDS

4.7. OTHER FIELDS

4.7.1. SUBJECT
4.7.2. COMMENTS
4.7.3. ENCRYPTED
4.7.4. EXTENSION-FIELD
4.7.5. USER-DEFINED-FIELD

5. DATE AND TIME SPECIFICATION

5.1. SYNTAX
5.2. SEMANTICS

6. ADDRESS SPECIFICATION

6.1. SYNTAX
6.2. SEMANTICS

6.2.1. DOMAINS
6.2.2. ABBREVIATED DOMAIN SPECIFICATION
6.2.3. DOMAIN TERMS
6.2.4. DOMAIN-DEPENDENT LOCAL STRING
6.2.5. BALANCING LOCAL-PART AND DOMAIN
6.2.6. MULTIPLE MAILBOXES
6.2.7. EXPLICIT PATH SPECIFICATION

6.3. RESERVED ADDRESS

7. BIBLIOGRAPHY
APPENDIX A. EXAMPLES

A.1. ADDRESSES
A.2. ORIGINATOR ITEMS
A.3. COMPLETE HEADERS

APPENDIX B. SIMPLE FIELD PARSING

B.1. SYNTAX
B.2. SEMANTICS

APPENDIX C. DIFFERENCES FROM RFC #733
APPENDIX D. ALPHABETICAL LISTING OF SYNTAX RULES

Original text document

### Preface

By 1977, the Arpanet employed several informal standards for the text messages (mail) sent among its host computers. It was felt necessary to codify these practices and provide for those features that seemed imminent. The result of that effort was Request for Comments (RFC) #733, "Standard for the Format of ARPA Network Text Message", by Crocker, Vittal, Pogran, and Henderson. The specification attempted to avoid major changes in existing software, while permitting several new features.

This document revises the specifications in RFC #733, in order to serve the needs of the larger and more complex ARPA Internet. Some of RFC #733's features failed to gain adequate acceptance. In order to simplify the standard and the software that follows it, these features have been removed. A different addressing scheme is used, to handle the case of inter-network mail; and the concept of re-transmission has been introduced.

This specification is intended for use in the ARPA Internet. However, an attempt has been made to free it of any dependence on that environment, so that it can be applied to other network text message systems.

The specification of RFC #733 took place over the course of one year, using the ARPANET mail environment, itself, to provide an on-going forum for discussing the capabilities to be included. More than twenty individuals, from across the country, participated in the original discussion. The development of this revised specification has, similarly, utilized network mail-based group discussion. Both specification efforts greatly benefited from the comments and ideas of the participants.

The syntax of the standard, in RFC #733, was originally specified in the Backus-Naur Form (BNF) meta-language. Ken L. Harrenstien, of SRI International, was responsible for re-coding the BNF into an augmented BNF that makes the representation smaller and easier to understand.

Next: 1. INTRODUCTION

Connected: An Internet Encyclopedia
RFC 822